User Guide

48
pH or mV value. Read the system time delay Tx on the time axis.
4. The deviation, Ti and Td can be calculated from the following:
• Deviation = Tx * max. slope (pH or mV)
• Ti = Tx / 0.4 (minutes)
• Td = Tx * 0.4 (minutes).
5. Set the above parameters and restart the system with the
controller in the loop. If the response has too much over-
shoot or is oscillating, then the system can be fine-tuned
slightly increasing or decreasing the PID parameters one
at a time.
Example:
the chart recording in the figure
aside was obtained continuously
dosing an alkaline solution to a
weak acid solution in a tank. The
initial settings will be:
Max. slope = 3 pH/5 mins = 0.6
pH/min
Time delay = Tx = approx. 7 mins
Deviation = Tx * 0.6 = 4.2 pH
Ti = Tx / 0.4 = 17.5 mins
Td = Tx * 0.4 = 2.8 mins
ALARM RELAY
The alarm relay functions in the following manner:
During normal operation (no alarm condition) the alarm re-
lay is energized; during an alarm condition or power failure
the relay will be de-energized. As long as a separate battery
power system is used an alarm will sound.
Example: High alarm set at 10 pH
Low alarm set at 4 pH
FS•O = NC (Normally Closed)
De-energized Relay
COM
FS•C = NO (Normally Open)
Energized Relay